package cn.ifxcode.utils;

import java.text.ParseException;  
import java.text.SimpleDateFormat;  
import java.util.Calendar;  
import java.util.Date;  
  
public class DateUtils {  
      
    static final String formatPattern = "yyyy-MM-dd";  
      
    static final String formatPattern_Short = "yyyyMMdd"; 
    
    static final String formatPattern_Long = "yyyy-MM-dd HH:mm:ss";
      
      
    /** 
     * 获取当前日期 
     * @return 
     */  
    public static String getCurrentDate(){  
        SimpleDateFormat format = new SimpleDateFormat(formatPattern_Short);        
        return format.format(new Date());  
    }  
      
    /** 
     * 获取制定毫秒数之前的日期 
     * @param timeDiff 
     * @return 
     */  
    public static String getDesignatedDate(long timeDiff){  
        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
        long nowTime = System.currentTimeMillis();  
        long designTime = nowTime - timeDiff;         
        return format.format(designTime);  
    }  
      
    /** 
     *  
     * 获取前几天的日期 
     */  
    public static String getPrefixDate(String count){  
        Calendar cal = Calendar.getInstance();  
        int day = 0-Integer.parseInt(count);  
        cal.add(Calendar.DATE,day);   // int amount   代表天数  
        Date datNew = cal.getTime();   
        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
        return format.format(datNew);  
    }  
    /** 
     * 日期转换成字符串 
     * @param date 
     * @return 
     */  
    public static String dateToString(Date date){  
        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
        return format.format(date);  
    }  
    /** 
     * 字符串转换日期 
     * @param str 
     * @return 
     */  
    public static Date stringToDate(String str){  
        //str =  " 2008-07-10 19:20:00 " 格式  
        SimpleDateFormat format = new SimpleDateFormat(formatPattern);  
        if(!str.equals("")&&str!=null){  
            try {  
                return format.parse(str);  
            } catch (ParseException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
            }  
        }  
        return null;  
    }  
      
    //java中怎样计算两个时间如：“21:57”和“08:20”相差的分钟数、小时数 java计算两个时间差小时 分钟 秒 .  
    public void timeSubtract(){  
        SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   
        Date begin = null;   
        Date end = null;   
        try {   
        begin = dfs.parse("2004-01-02 11:30:24");   
        end = dfs.parse("2004-03-26 13:31:40");   
        } catch (ParseException e) {   
        e.printStackTrace();   
        }   
  
        long between = (end.getTime() - begin.getTime()) / 1000;// 除以1000是为了转换成秒   
  
        long day1 = between / (24 * 3600);   
        long hour1 = between % (24 * 3600) / 3600;   
        long minute1 = between % 3600 / 60;   
        long second1 = between % 60;   
        System.out.println("" + day1 + "天" + hour1 + "小时" + minute1 + "分"   
        + second1 + "秒");   
    }  
  
}  